class Packet;
    rand bit [31:0] src;
    constraint c1 {
        src > 10 ;
        src < 15;
    }
endclass

module testbench;
    Packet p; 
    initial begin
        $display("\t\t\033[32m\t start testbench");
        for (int i = 0; i < 10; i++) begin
            p = new();
            assert (p.randomize()); 
            $display(p.src);
        end
        $display("\t\t\t  end  testbench\033[0m");
    end
endmodule
